- Found at DESTRUCT-IVE and CONTRUCT-IVE plate margins.
- Destructive Margins
- Here the oceanic plate goes under the continental plate because its more dense.
- The oceanic plate moves down into the mantle, where its melted and destroyed. A pool of magma forms. The magma rises through cracks in the crust called vents. The magma erupts onto the surface (lava) forming a volcano.
- Constructive Margins
- Here the magma rises up into the gap created by the plates moving apart, forming a volcano.
- Some volcanoes also form over parts of the mantle that are really hot (called hotspots) eg in Hawaii.